Methods and apparatuses of the types described hereinbefore are being used to an ever inceasing extent for the manufacture of bottom-fold bags, more particularly those made of an endless tubular synthetic material, for example high-pressure polyethylene. Forming the bottom-flaps serves, among other things, to provide a base whuch is as rectangular as possible, so that the bag remains upright after it has been filled. This makes it easier to store the filled bag and, especially, a bag which has already been opened by the consumer. There is, however, a difficulty in the case of known bottom-fold bags, in which the bottom flap layers are not connected together, but are merely pressed together by the product in the bag, in that, especially in the case of a product of little internal consistency, for example animal litter, granular materials, and other freely flowing goods, the bottom tends not to retain its flat configuration in a satisfactory manner, so that the bag does not stand very well.
U.S. Pat. No. 3,739,977 discloses a method of the type mentioned at the beginning hereof in which the triangular, double-walled bottom-flaps are connected together at the four corners of the lateral walls. Similar methods and bottom-fold bags are also known from U.S. Pat. Nos. 3,772,116 and 4,230,030. U.S. Pat. Nos. 4,079,662 and 4,365,459 also disclose apparatuses of the above type for the production of bottom-fold bags. It has been found, however, that the methods, apparatuses and bags in question do not satisfactorily meet the requirements of inexpensive production of bottom-fold bags, with a reliably flat configuration of the standing surface, especially in the case of freely flowing goods. A side-fold bag, disclosed in German Patent No. 830,157, in which the bottom flaps are glued to the bottom part, is also unsatisfactory in this respect.